[1]} convincingly showed that SN 2010lp displayed a nebular spectrum closely resembling that of SN 1991bg about 200 days after maximum. The main difference was the absence of the narrow [Fe iii] lines. These were replaced by two narrow (full width at half maximum \(\approx 1900\)  km s\(^{-1}\) ) emissions which correspond to [O i] 6300, 6363 Å, with a blue- and a red-shifted component. [2]} showed that the higher ionization [Fe iii] lines in SN 1991bg are emitted from a small volume, presumably at the centre of the ejecta, bounded by a velocity of \(\sim 3000\)  km s\(^{-1}\) . A low central density was likely to be responsible for the high ionization.
